The present invention relates to a gas heater, a gas supply apparatus and a method of providing gas.
In a conventional gas supply system, typically, a high-pressure gas source is connected to a gas pressure regulator. The gas pressure regulator is operable to regulate a reduction in the pressure of gas from the high-pressure at which the gas was stored at source to a desired working pressure. Typically, gas is stored in high pressure cylinders at pressures of approximately 200 bar. Commonly available regulators have been designed to operate at this level of intake gas pressure.
Recently, gas has been provided at higher pressures from within cylinders. For example, it is now possible to obtain 300 bar pressure gas cylinders. Manufacturers of pressure regulators were requested to offer 300 bar regulators using similar designs as those used for 200 bar input pressures. The difference between the regulators for operating at 300 bar compared to those designed to operate at 200 bar is the input pressure range on the gauges, and that an adapted valve control unit is required having a stronger spring or a diaphragm.
As gas expands it is known to undergo the Joule-Thomson effect, i.e. the cooling of a gas as it expands. The reduction in temperature as gas expands is related to the change in pressure of the gas. If initially the gas is at a higher pressure (for example of about 300 bar as opposed to a pressure of about 200 bar), and in both cases the gas is regulated to the same working pressure (for example about 10 bar), the gas that started at higher pressure (300 bar) will be substantially cooler than that that started at the lower pressure. Thus, the temperature of a pressure regulator becomes much lower in comparison when the input pressure of gas received by it is for example about 300 bar as opposed to about 200 bar.
In fact, this higher-pressure effect, starts to be prominent at above about 240 bar and it is further amplified by lower ambient temperatures. It is not uncommon in such situations for the pressure regulator to freeze. This can render the pressure regulator useless. Alternatively, problems such as output flow oscillation, blocking of regulator functionality and resulting leakage can occur.
There are known systems that have been developed in attempts to address this problem. One type of system relies on heating the gas at high pressure between the gas source and the pressure regulator. This is done by directing the gas through a length of straight or coiled tube which is heated. However, such systems are unable to provide sufficient heat to the gas without becoming either dangerously hot themselves or requiring unfeasibly long lengths of tubing.
An alternative attempt at a solution to this problem has been to heat the pressure regulator directly so that as gas passes through it and cools due to the Joule-Thomson effect, the temperature of the regulator device does not go below a lowest possible working temperature of the regulator. In other words, the regulator is heated so that the problems described above are moderated but still encountered.
Again, such attempts to solve the problem identified above have been unsuccessful. In particular, both the above mentioned attempts at a solution to this problem have low efficiency. This means that even if large amounts of input energy are used, with the intention of increasing the temperature of the gas sufficiently, it has not been possible to ensure that problems with the regulator do not occur.
United States Patent Application No. 2003/0154700 discloses a module for use as a filter, catalytic converter or heater.
According to a first aspect of the present invention there is provided a gas heater for connection to a heat source and a pressurised gas source, the gas heater comprising: a jacket having a gas inlet and a gas outlet and defining a cavity therebetween; and, a porous heat exchanger extending within said cavity, from said inlet to said outlet; and a heat provider for providing heat to said heat exchanger along the length thereof.